1. Field of the Invention
The present invention relates to a needle blow nozzle, an air cooling method and apparatus, a blow molding method and apparatus, and a blow molded product. More particularly, the present invention relates to a novel improvement in that a needle portion at the tip of a needle blow nozzle is formed into an umbrella-like shape having an acute apical angle and a larger diameter, thus enabling the larger-diameter needle blow nozzle to be laterally inserted into a parison with certainty and a large amount of cooling air to be supplied and discharged, whereby the parison cooling ability is increased and the molding cycle is shortened.
2. Description of the Related Art
FIGS. 1 and 2 show one example of a blow molding apparatus, disclosed in Japanese Unexamined Patent Publication No. 6-182866, which employs a conventional needle blow nozzle (often called a lateral blow nozzle) of the above-mentioned type. Referring to FIGS. 1 and 2, numeral 1 denotes a needle blow nozzle having a tubular body 4. A slope 11 is formed at the tip of the tubular body 4 by obliquely cutting the tubular body 4. In other words, the nozzle tip is constructed into a similar shape as a syringe needle used in medical treatment. The tubular body 4 has a penetration bore 4aA formed therethrough for communicating with a nozzle hole 20 of the slope 11.
The conventional needle blow nozzle of the blow molding apparatus, constructed as described above, has problems below.
The tip of the conventional needle blow nozzle has a shape resulted from simply obliquely cutting the tubular body 4. Viewing the slope at the nozzle tip from the axial direction, the nozzle hole is largely opened and therefore a tip shape of a needle inserted into a parison from its outer surface is not dot-like but linear. Thus resistance against insertion of the needle into the parison has increased, it is not easy to insert the needle into the parison. For this reason, the nozzle diameter has a maximum limit at 8 mm. The nozzle having an 8 mm diameter however cannot quickly provide a large amount of cooling air into a molded product. Another method of pinching upper and lower portions of a parison and piercing air nozzles through pinched portions (59c, 59d; see FIG. 9) is disadvantageous in that the wall thickness of the pinched portions must be increased to compensate for a reduction of strength, the shape of the pinched portions is complicated, and the molding cycle is prolonged.
Generally, as a parison under molding is cooled more rapidly, the molding cycle is more shortened and the production efficiency is more increased. It is however difficult to increase the diameter of the conventional needle blow nozzle because an increase of the diameter makes it harder to insert the nozzle. In spite of such a difficulty, there has been a demand in the field of relevant art for cooling a molded product in a shorter time and reducing the molding cycle by employing a larger-diameter needle spray nozzle.
With the view of solving the problems set forth above, an object of the present invention is to provide a needle blow nozzle, an air cooling method and apparatus, a blow molding method and apparatus, and a blow molded product, with which a needle portion at the tip of the needle blow nozzle is formed into an umbrella-like shape having an acute apical angle and a larger diameter, thus enabling the larger-diameter needle blow nozzle to be laterally inserted into a parison with certainty and a large amount of cooling air to be supplied and discharged, whereby the parison cooling ability is increased and the molding cycle is shortened.
To achieve the above object, the present invention provides a needle blow nozzle having an elongate tubular body, the nozzle being laterally inserted into a parison held between a pair of molds for blow molding, and jetting air to the interior of the parison, wherein a needle portion formed at a fore end of the tubular body has a needle center positioned at an axis of the tubular body, slopes providing edges extending at an acute angle are formed to extend from the needle center toward an outer peripheral surface of the tubular body, and nozzle holes are formed in the needle portion. At least two elongate cutting areas extending in the axial direction are formed in the slopes, fore ends of the elongate cutting areas are converged to the needle center, and the nozzle holes are positioned between the elongate cutting areas. Also, the present invention provides an air cooling method comprising the steps of attaching a cap-like circulation jig to a needle portion of a needle blow nozzle provided at a side of at least one of a pair of molds for blow molding, supplying high-pressure air from a high-pressure air source to the needle blow nozzle through an air cooling apparatus in a circulating manner, and pre-cooling the high-pressure air prior to closing the molds. Further, the present invention provides an air cooling apparatus comprising a needle blow nozzle provided at a side of at least one of a pair of molds for blow molding, a cap-like circulation jig detachably attached to a needle portion of the needle blow nozzle, an air cooling apparatus connected to the needle blow nozzle, and a high-pressure air source connected to the air cooling apparatus and supplying high-pressure air, the high-pressure air being circulated through the air cooling apparatus to pre-cool a high-pressure air circuit while the circulation jig is held attached to the needle portion. Still further, the present invention provides a blow molding method comprising the steps of laterally inserting a needle blow nozzle into a parison held between molds for blow molding, jetting air to the interior of the parison, and producing a blow molded product, wherein the air is supplied to the parison while being cooled with an air cooling apparatus and adiabatic expansion of high-pressure air. Still further, the present invention provides a blow molding method comprising the steps of piercing a needle blow nozzle into a parison held between molds, and producing a molded product, wherein a driving circuit for driving the needle blow nozzle to pierce the parison is operated at a high speed by increasing the pressure from a driving source, increasing an air flow rate through a solenoid valve, flow passages of hoses and a silencer, and providing a reservoir tank to compensate for deficiency of pressure supply from the driving source. Still further, the present invention provides a blow molding apparatus for molding a blow molded product by laterally inserting a needle blow nozzle into a parison held between a pair of molds for blow molding, and jetting air to the interior of the parison, wherein an air cooling apparatus is connected to the needle blow nozzle. In the above blow molding apparatus, a needle portion formed at a fore end of a tubular body of the needle blow nozzle has a needle center positioned at an axis of the tubular body, slopes providing edges extending at an acute angle are formed to extend from the needle center toward an outer peripheral surface of the tubular body, and nozzle holes are formed in the needle portion. In addition, at least two elongate cutting areas extending in the axial direction are formed in the slopes, fore ends of the elongate cutting areas are converged to the needle center, and the nozzle holes are positioned between the elongate cutting areas. Still further, the present invention provides a blow molded product having one or more mouths, wherein the mouths are partly cut off to remove holes formed therein. Still further, the present invention provides a blow molded product produced with blow molding by injecting air into a parison held between molds through a needle blow: nozzle, wherein air is injected into the parison through the needle blow nozzle provided at a side of the molds, and holes used for injecting the air are formed in mouths formed on the blow molded product during the blow molding of the parison.